Bug 818545 - Gracefully handle errors when loading mozconfigs; r=glandium

DONTBUILD (NPOTB)

python/mozbuild/mozbuild/base.py

@@ -2,7 +2,7 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-from __future__ import unicode_literals
+from __future__ import print_function, unicode_literals
 
 import logging
 import os
@@ -14,7 +14,11 @@ from mach.mixin.logging import LoggingMixin
 from mach.mixin.process import ProcessExecutionMixin
 
 from .config import BuildConfig
-from .mozconfig import MozconfigLoader
+from .mozconfig import (
+    MozconfigFindException,
+    MozconfigLoadException,
+    MozconfigLoader,
+)
 
 
 class MozbuildObject(ProcessExecutionMixin):
@@ -244,3 +248,27 @@ class MachCommandBase(MozbuildObject):
     def __init__(self, context):
         MozbuildObject.__init__(self, context.topdir, context.settings,
             context.log_manager)
+
+        # Incur mozconfig processing so we have unified error handling for
+        # errors. Otherwise, the exceptions could bubble back to mach's error
+        # handler.
+        try:
+            self.mozconfig
+
+        except MozconfigFindException as e:
+            print(e.message)
+            sys.exit(1)
+
+        except MozconfigLoadException as e:
+            print('Error loading mozconfig: ' + e.path)
+            print('')
+            print(e.message)
+            if e.output:
+                print('')
+                print('mozconfig output:')
+                print('')
+                for line in e.output:
+                    print(line)
+
+            sys.exit(1)
+

python/mozbuild/mozbuild/mozconfig.py

@@ -26,6 +26,12 @@ supported. Please move it to %s/.mozconfig or set an explicit path
 via the $MOZCONFIG environment variable.
 '''.strip()
 
+MOZCONFIG_BAD_EXIT_CODE = '''
+Evaluation of your mozconfig exited with an error. This could be triggered
+by a command inside your mozconfig failing. Please change your mozconfig
+to not error and/or to catch errors in executed commands.
+'''.strip()
+
 
 class MozconfigFindException(Exception):
     """Raised when a mozconfig location is not defined properly."""
@@ -37,8 +43,9 @@ class MozconfigLoadException(Exception):
     This typically indicates a malformed or misbehaving mozconfig file.
     """
 
-    def __init__(self, path, message):
+    def __init__(self, path, message, output=None):
         self.path = path
+        self.output = output
         Exception.__init__(self, message)
 
 
@@ -173,8 +180,22 @@ class MozconfigLoader(ProcessExecutionMixin):
         args = self._normalize_command([self._loader_script, self.topsrcdir,
             path], True)
 
-        output = subprocess.check_output(args, stderr=subprocess.PIPE,
-            cwd=self.topsrcdir, env=env)
+        try:
+            # We need to capture stderr because that's where the shell sends
+            # errors if execution fails.
+            output = subprocess.check_output(args, stderr=subprocess.STDOUT,
+                cwd=self.topsrcdir, env=env)
+        except subprocess.CalledProcessError as e:
+            lines = e.output.splitlines()
+
+            # Output before actual execution shouldn't be relevant.
+            try:
+                index = lines.index('------END_BEFORE_SOURCE')
+                lines = lines[index + 1:]
+            except ValueError:
+                pass
+
+            raise MozconfigLoadException(path, MOZCONFIG_BAD_EXIT_CODE, lines)
 
         parsed = self._parse_loader_output(output)
 
@@ -245,7 +266,7 @@ class MozconfigLoader(ProcessExecutionMixin):
         current_type = None
         in_variable = None
 
-        for line in output.split('\n'):
+        for line in output.splitlines():
             if not len(line):
                 continue
 

python/mozbuild/mozbuild/test/test_mozconfig.py

@@ -17,6 +17,7 @@ from tempfile import (
 
 from mozbuild.mozconfig import (
     MozconfigFindException,
+    MozconfigLoadException,
     MozconfigLoader,
 )
 
@@ -296,3 +297,18 @@ class TestMozconfigLoader(unittest.TestCase):
             self.assertIn('EMPTY', result['env']['added'])
             self.assertEqual(result['env']['added']['EMPTY'], '')
 
+    def test_read_load_exception(self):
+        """Ensure non-0 exit codes in mozconfigs are handled properly."""
+        with NamedTemporaryFile(mode='w') as mozconfig:
+            mozconfig.write('echo "hello world"\n')
+            mozconfig.write('exit 1\n')
+            mozconfig.flush()
+
+            with self.assertRaises(MozconfigLoadException) as e:
+                self.get_loader().read_mozconfig(mozconfig.name)
+
+            self.assertTrue(e.exception.message.startswith(
+                'Evaluation of your mozconfig exited with an error'))
+            self.assertEquals(e.exception.path, mozconfig.name)
+            self.assertEquals(e.exception.output, ['hello world'])
+